1. Field of the Invention
This invention relates generally to the field of hard disk drives. More particularly, the invention relates to hard disk drives having at least one flow modification element disposed adjacent to at least one data storage disk.
2. Discussion of the Related Art
Conventional hard disk drive 100, a portion of which is shown in FIG. 1, includes at least one rotating disk 110 on which data is stored in concentric tracks. Disk drive 100 includes read-write head 120 disposed on aerodynamically operable slider assembly 130 and back plate 140. Slider assembly 130 is disposed at the end of the actuator arm portion of actuator assembly 160. Disk 110 couples with spindle 170 to rotate in a counterclockwise direction (shown as “A” in FIG. 1), thereby causing airflow in direction A. The airflow impinges upon portions of actuator assembly 160 and slider assembly 130. Movement of actuator assembly 160 is accomplished using a conventional voice coil motor (not shown in FIG. 1).
Head 120 reads data from and writes data to approximately concentric data tracks 210, shown schematically in FIG. 2. While disk drive 100 is in operation, actuator assembly 160 experiences cross-track motion 220 as head 120 attempts to follow track 210.
Cross track motion 220 of head 120 can be measured as track misregistration (TMR). Larger levels of TMR limit the amount of data that can be written to and retrieved from disk drive 100. Cross track motion 220 results from several disturbances that couple into head 120. Some of the major disturbances include disk vibration, spindle bearing runout (repeatable and non-repeatable), slider assembly 130 vibration, actuator arm vibration, and drive enclosure vibration.
In order to accurately read and write data, a servo control system is employed to keep head 120 aligned with track 210. The servo control system has its own attenuation and amplification characteristics, and is typically ineffective above about 4 kHz. Head 120 vibration spectrums for conventional disk drives 100 exhibit substantial vibrational movement of head 120 in a high frequency region of around 5 to 25 kHz. The servo control system is ineffective in compensating for the vibration in the high frequency region.
A common approach to increase the storage capacity of a disk drive 100 is to increase the track 210 density (tracks per inch, or TPI). Due to the continuing push for greater track 210 densities, allowable cross track motion 220 is decreasing in absolute terms. However, drives are spinning at higher speeds. Higher speeds increase the amount of cross track motion 220 of head 120. The increase in TMR (i.e., cross track motion 220) in the high frequency region is more pronounced at higher disk rotation speeds. A drive is typically designed so that the total TMR cannot exceed a certain limit (e.g., approximately ten percent of the track 210 width). As a result of this limit, at higher rotational speeds, no remaining TMR budget is available at the higher rotational frequencies, and the vibrational energy within the TMR spectral bandwidth of 0-25 kHz frequency range needs to be minimized in order to provide error-free operation of disk drives 100.
Disk drives 100 are known to those skilled in the art. For example, a conventional disk drive 100, such as the disk drive described by U.S. Pat. No. 5,526,203, can include baffle 190 disposed adjacent to upstream from actuator assembly 160. Baffle 190 is placed adjacent to the outermost diameter of disks 110. According to the U.S. Pat. No. 5,526,203 patent, one motivation for using baffles 190 is to block contaminants generated by actuator assembly 160 from being deposited on disks 110. Baffles 190 have the unintended effect of blocking airflow that would otherwise impinge on portions of actuator assembly 160 disposed outside outer edges 240 of disks 110. Such airflow blocking can reduce TMR in some designs.
However, baffles 190 cannot effectively reduce the airflow contributions (or momentum transfer) that cause cross track motion 220. Baffles 190 do not modify the airflow interaction with portions of actuator assembly 160 disposed between disks 110. Therefore, what is required is a solution that reduces the momentum transfer caused by airflow impinging these portions of actuator assembly 160 adjacent to disk 110 data surfaces. The reduction of momentum transfer decreases cross track motion 220 of head 120. Heretofore, the requirement of reduced cross track motion 220 referred to above has not been fully met.